Yesterday former Massachusetts Gov. Mitt Romney launched the first negative TV ad of the 2008 cycle, hammering former Arkansas Gov. Mike Huckabee in Iowa for having "supported in-state tuition benefits for illegal immigrants" and "taxpayer-funded scholarships for illegal aliens."

While a valid critique (Huckabee has never denied Romney's assertions), it was an odd maneuver. Obviously, Romney's campaign is concerned about Huckabee rising in the polls -- especially in Iowa, where caucus night is less than a month away. But launching the ad meant Romney is attacking on what is, at best, shaky ground. Although he did veto a bill offering in-state tuition to illegal immigrants, Romney has hardly been an immigration hawk. In November 2005, in an interview with the Boston Globe, he characterized comprehensive immigration reform proposals, such as those preferred by Arizona Sen. John McCain and President Bush, as "reasonable" and "quite different" from amnesty. He also was discovered last week to still have illegal immigrants tending to his property -- fully a year after his employment of a landscaping firm using undocumented workers was first exposed.

Perhaps that's why yesterday -- the same day on which Romney released his ad -- Jim Gilchrist, founder of the Minuteman Project, chose to endorse a different candidate: Huckabee, no less. His backing of the onetime pastor, currently running 10 points ahead of Romney in Iowa according to the Real Clear Politics average, is clearly a smack in the face for Romney. But it's a major roadblock, to boot. How exactly can Romney attack Huckabee on immigration, when the hero of the border enforcement crowd has given him the thumbs up? More to the point, if Romney cannot, how else can he try to pare back the Arkansan's lead in a state that, for him, is must-win? Surely, he must -- but having put immigration front and center makes pivoting to discuss other issues tricky, to the extent it is even possible in the first place.

Romney and his team are well aware that seeking to swipe at Huckabee on social and moral issues is a non-starter. Huckabee possesses impeccable credentials where opposition to abortion and gay marriage, and support for constitutional amendments dealing with both matters, are concerned. There are, quite simply, no gaps in Huckabee's social conservative armor -- whereas, of course, there are plenty in Romney's, despite the positions he currently espouses. Pope Benedict XVI would struggle to get to Huckabee's right on values items in this campaign. A formerly pro-choice, gay-friendly governor from the most liberal state in the nation is hardly going to manage it.

Of course, Romney could attack Huckabee on fiscal matters. In fact, his campaign attempted to do just that yesterday following the ad's release and Gilchrist's endorsement, commenting that Huckabee's record of "more taxes, more spending" (and, staying on topic, "weak border security") was "at odds" with the GOP's core values. But this too presents risks. Not only has the Club for Growth been attacking Huckabee for a long while for his tax-friendliness and alleged big government enthusiasm, to apparently minimal effect in Iowa (which is already serving as Huckabee's launch-pad to success). More critically, attacks on Huckabee's tax-and-spend ways are unlikely to benefit Romney, specifically.

This is not because of a lack of clear contrast between the two candidates where economic issue positions (and records) are concerned, but rather because of Romney's positioning in this race. Having spent months touting his "three-legged-stool" appeal (i.e., as just as much a social/moral issues conservative as a defense/foreign policy hawk or a free-marketeer), his calling card is not that of "economic conservative" per se.

By contrast, that is the defining characteristic of his opponent, ex-New York City Mayor Rudy Giuliani. By most accounts, Giuliani earned more glowing praise from the Club for Growth for his economic record than did Romney, and just last week, the group praised his promotion of school choice prominently on its website. Meanwhile, Giuliani is also looking more and more like the choice for staunch tax-cutters and budget-slashers thanks to last week's big thumbs up from Grover Norquist of Americans for Tax Reform. Following the CNN/YouTube debate, in which Giuliani pledged to oppose tax increases, Norquist not only stated that "in looking at the records of all the Republican candidates," Giuliani's "clearly stands out," but also that he is "the most successful tax cutter in the Republican field today." This presents a neat quandary for Romney. If he convinces voters that Huckabee is a bad-news economic populist, will he simultaneously give them a reason to back his other chief rival -- who, incidentally, possesses greater fundraising strength than the Arkansan, and occupies the third place position in Iowa according to several recent polls?

Romney and his advisers are smart enough to know that the answer to that question may just be "yes." But if they want to avoid an embarrassing defeat in Iowa -- one that could diminish their chances elsewhere -- attacking Huckabee on taxes and spending may now be their only hope, no matter the risks. One thing is for certain: victory in Iowa can no longer come easily for Romney -- and if it comes at all, a hefty price tag, in the form of empowering other rivals, may well be attached.